The present invention relates to a coordinate input apparatus for detecting the position pointed on the coordinate input surface and inputting the detected coordinate value, and its control method.
In general, a coordinate input apparatus can be roughly classified into two types, i.e., a touch panel with which the user directly makes operation input on the input surface using his or her finger, and a digitizer with which the user makes coordinate input on the input surface by operating a tool such as a pen or the like. The digitizer does not normally allow direct input operation with the finger. On the other hand, the touch panel also allows input operation using an input pointer such as a pen or the like (the input pointer used for the digitizer will be generally referred to as a pen hereinafter). Hence, the touch panel is convenient: simple input operation can be done by directly pointing the input surface with the finger, and precise input operation of characters, graphics, and the like can be done by the pen.
However, when the user makes input operation on the touch panel by operating a tool such as a pen or the like, if his or her hand touches the input surface, the touched portion is unwantedly detected as the pointed position, resulting in operation errors. Also, in case of, e.g., an optical type apparatus that detects the pointed input not only when an object contacts but when it approaches, for example, an original placed on the input surface is detected as the pointed input, thus producing input errors. Especially, since display devices tend to have larger screens (i.e., larger input surfaces), the above-mentioned problems can no longer be ignored.
The input operation by the finger or the like need be done by a light operation force although low resolution is allowed (such input operation will be referred to as a touch input hereinafter). By contrast, the input operation using a pen can have a certain writing pressure but requires high resolution (such input operation will be referred to as a pen input hereinafter) Especially, character recognition requires very high resolution. It is very difficult to simultaneously meet these two antithetic requirements. Especially, as for the resolution, the same applies not only to spatial resolution but also to temporal resolution, and the specification difference required for touch and pen inputs is very large. Hence, it is nearly impossible to satisfy these requirements by a single detection method.
In recent years, energy savings are required for information processing apparatuses, and it is getting harder to attain energy savings and higher resolution.